[PATCH] Fix tree-loop-distribution.c ICE with -ftrapv (PR tree-optimization/89278)

[Bin.Cheng]

On Fri, Feb 15, 2019 at 6:52 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> Hi!
>
> The following testcase ICEs, because we try to gimplify a complex expression
> that with -ftrapv wants to emit multiple bbs.  Fixed by using
> rewrite_to_non_trapping_overflow.  Bootstrapped/regtested on x86_64-linux
So with what condition we can safely rewrite trapping operations into
non trapping one?  Does the rewrite nullify -ftrapv which requires
trap behavior?

Thanks,
bin
> and i686-linux, ok for trunk and 8.3?
>
> 2019-02-14  Richard Biener  <rguenther@suse.de>
>             Jakub Jelinek  <jakub@redhat.com>
>
>         PR tree-optimization/89278
>         * tree-loop-distribution.c: Include tree-eh.h.
>         (generate_memset_builtin, generate_memcpy_builtin): Call
>         rewrite_to_non_trapping_overflow on builtin->size before passing it
>         to force_gimple_operand_gsi.
>
>         * gcc.dg/pr89278.c: New test.
>
> --- gcc/tree-loop-distribution.c.jj     2019-01-10 11:43:02.255576992 +0100
> +++ gcc/tree-loop-distribution.c        2019-02-14 12:17:24.403403131 +0100
> @@ -114,6 +114,7 @@ along with GCC; see the file COPYING3.
>  #include "tree-scalar-evolution.h"
>  #include "params.h"
>  #include "tree-vectorizer.h"
> +#include "tree-eh.h"
>
>
>  #define MAX_DATAREFS_NUM \
> @@ -996,7 +997,7 @@ generate_memset_builtin (struct loop *lo
>    /* The new statements will be placed before LOOP.  */
>    gsi = gsi_last_bb (loop_preheader_edge (loop)->src);
>
> -  nb_bytes = builtin->size;
> +  nb_bytes = rewrite_to_non_trapping_overflow (builtin->size);
>    nb_bytes = force_gimple_operand_gsi (&gsi, nb_bytes, true, NULL_TREE,
>                                        false, GSI_CONTINUE_LINKING);
>    mem = builtin->dst_base;
> @@ -1048,7 +1049,7 @@ generate_memcpy_builtin (struct loop *lo
>    /* The new statements will be placed before LOOP.  */
>    gsi = gsi_last_bb (loop_preheader_edge (loop)->src);
>
> -  nb_bytes = builtin->size;
> +  nb_bytes = rewrite_to_non_trapping_overflow (builtin->size);
>    nb_bytes = force_gimple_operand_gsi (&gsi, nb_bytes, true, NULL_TREE,
>                                        false, GSI_CONTINUE_LINKING);
>    dest = builtin->dst_base;
> --- gcc/testsuite/gcc.dg/pr89278.c.jj   2019-02-14 12:18:38.778173413 +0100
> +++ gcc/testsuite/gcc.dg/pr89278.c      2019-02-14 12:18:19.065499344 +0100
> @@ -0,0 +1,23 @@
> +/* PR tree-optimization/89278 */
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -ftrapv -ftree-loop-distribute-patterns --param max-loop-header-insns=2" } */
> +
> +void
> +foo (int *w, int x, int y, int z)
> +{
> +  while (x < y + z)
> +    {
> +      w[x] = 0;
> +      ++x;
> +    }
> +}
> +
> +void
> +bar (int *__restrict u, int *__restrict w, int x, int y, int z)
> +{
> +  while (x < y + z)
> +    {
> +      w[x] = u[x];
> +      ++x;
> +    }
> +}
>
>         Jakub